well the one piece of advice i can give you is to never, ever buy boot online because all boots are made/sized differently and they need to fit your feet perfectly. if the sports authority boots fit you perfect, go for it, if not go somewhere else and try on boots to get a perfect fit. boots are one thig you shouldnt skimp on.
On the other gear, If you just want SOMETHING, then I guess its ok, btu without models this whole post is really useless.
does your brother have more than one board? more specifically, can you always ride his burton? If you can I would say just get some GOOD boots, and with time buy your bindings and board. the end of the season is THE BEST time for that, and I buy all my new gear at that time as well. you can get some killer boards and bindings for amazing prices...